1. Field of the Invention
Example embodiments of the present invention relate generally to semiconductor devices and methods of fabricating the same, and more particularly, to fuse regions of a semiconductor memory device and methods of fabricating the same.
2. Description of the Related Art
Memory devices (i.e., semiconductor memory chips) formed at a semiconductor substrate may be electrically tested prior to an assembly process to determine whether the semiconductor memory chips are damaged or not. When the test determines a damaged chip(s), the damaged chip may operate abnormally due to at least one failed cell. The failed cells may be replaced with redundant cells using a repair process. The repair process may include an irradiating procedure with an irradiating device, such as a laser beam, by blowing predetermined fuses so that some of the redundant cells may include addresses of the failed cells in a write mode and/or a read mode. The fuses may be formed of conductive material layers comprising, for example, a doped poly silicon layer, an aluminum layer, a tungsten silicide layer and/or a tungsten layer.
As semiconductor devices become more highly integrated, distances between the fuses may be gradually reduced. However, the reduced distance between the fuses may cause damage during the repair process. In other words, in the event that one of the selected fuses is blown using a laser beam, the non-selected fuses adjacent to the selected fuse may be damaged due to the laser beam.
FIG. 1 is a cross-sectional view illustrating a fuse region in a conventional art.
Referring to FIG. 1, a pair of first fuse wires 2a and 2b and a pair of second fuse wires 3a and 3b may be provided in a tetra-ethyl-ortho-silicate (TEOS) oxide layer 8. The second fuse wires 3a and 3b may be located at a lower level than the first fuse wires 2a and 2b. Also, the second fuse wires 3a and 3b may be located below regions between the first fuse wires 2a and 2b. In addition, the TEOS oxide layer 8 may have protrusions P located over the second fuse wires 3a and 3b. As a result, recessed grooves G may be provided between the protrusions P.
In order to selectively blow one of the first fuse wires 2a and 2b, a laser beam should be irradiated onto selected fuse wire 2a, for example. However, if the laser beam is misaligned with the selected first fuse wire 2a, the laser beam may be irradiated elsewhere including the protrusion P adjacent to the selected first fuse wire 2a. In this case, when energy of the laser beam is not precisely controlled, the second fuse wire 3a adjacent to the selected first fuse wire 2a may be damaged due to the laser beam.
FIG. 2 is a cross-sectional view illustrating a fuse region disclosed in the conventional art.
Referring to FIG. 2, a pair of first fuse wires 12a and 12b and a pair of second fuse wires 13a and 13b may be provided in a TEOS oxide layer 18 which may have the same structure as shown in FIG. 1. The TEOS oxide layer 18 also may have protrusions P′ located over the second fuse wires 13a and 13b. Thus, recessed grooves G′ may be provided between the protrusions P′. In addition, cover patterns 20b and 20d may be disposed on the protrusions P′. The cover patterns 20b and 20d may be composed of, for example, a metal layer to increase a blocking effect of a laser beam.
In order to selectively blow one of the first fuse wires 12a and 12b, a laser beam 17a should be irradiated onto selected fuse wire 12a, for example. If the laser beam 17a is misaligned with the selected first fuse wire 12a, as shown in FIG. 2, an edge of the cover pattern 20b adjacent to the selected fuse wire 12a may be exposed to the laser beam 17a. However, in this case, even though the laser beam 17a may be irradiated onto the edge of the cover pattern 20b due to a misalignment of the laser beam 17a, the cover pattern 20b may reduce and/or prevent the second fuse wire 13a adjacent to the selected first fuse wire 12a from being damaged by the laser beam 17a. 
As described above, the cover patterns 20b and 20d may prevent the second fuse wires 13a and 13b from being damaged by the misaligned laser beam. However, when the protrusions (P in FIG. 1 and P′ in FIG. 2) and the cover patterns 20b and 20d are misaligned with the second fuse wires 13a and 13b, the second fuse wires 13a and 13b may still be damaged by the misaligned laser beam.
FIG. 3 is a cross-sectional view illustrating a fuse region disclosed in the conventional art, in which several drawbacks will be discussed.
Referring to FIG. 3, the laser beam 17a may be irradiated onto the first fuse wire 12a to selectively blow the first fuse wire 12a as described with reference to FIG. 2. When the laser beam 17a is irradiated onto the edge of the cover pattern 20b due to the misalignment of the laser beam 17a, a portion 20b′ of the cover pattern 20b may be detached away from a surface of the TEOS oxide layer 18 as shown in FIG. 3. The detached cover pattern 20b′ may then be re-adsorbed to a surface of the semiconductor substrate having the fuse region to act as a contaminant. In other words, when the detached cover pattern 20b′ is re-adsorbed to a region between the adjacent interconnection lines, the detached cover pattern 20b′ may electrically connect the adjacent interconnection lines to each other, thereby causing an abnormal operation of the semiconductor device.
In addition, when the laser beam 17a is misaligned with the selected first fuse wire 12a, for example, the selected first fuse wire 12a in a region onto which the laser beam 17a is irradiated may not be completely blown. As a result, as shown in FIG. 3, a fuse residue 12a′ may remain in the irradiation region of the laser beam 17a. This event may be due to an adhesion between the selected first fuse wire 12a and the TEOS oxide layer 18 as well as a weak irradiation energy at the edge of the laser beam 17a. 